With the spread of electronic appliances including office automation apparatuses and communication instruments, electromagnetic wave emission from these appliances have come into a problem. That is, adverse effect of electromagnetic wave to the human body is feared and it is also a problem that the electromagnetic wave affects precision apparatus to cause malfunction.
Therefore, plates having good electromagnetic-wave shielding efficiency and light transparency have developed as front filters for PDPs of the office automation apparatuses and come into commercial use. Such plates are also used as windows of a place where a precision apparatus is installed, such as a hospital or a laboratory in order to protect the precision apparatus from electromagnetic waves form a portable telephone.
A conventional electromagnetic-wave shielding and light transmitting plate typically comprises transparent base plates such as acrylic boards and a conductive mesh member like a wire netting and is formed by interposing the conductive mesh member between the transparent base plates and by assembling them.
In order to provide good electromagnetic-wave shielding efficiency when such an electromagnetic-wave shielding and light transmitting plate is assembled in a body of an equipment such as PDP, it is necessary to provide uniform current conduction between the electromagnetic-wave shielding and light transmitting plate and the body of the equipment, that is, between the conductive mesh of the electromagnetic-wave shielding and light transmitting plate and a conduction surface of the body.
A structure, which can provide good current conduction between an electromagnetic-wave shielding and light transmitting plate and a body of an equipment with a simple structure, has conventionally proposed (JPA 9-147752). This structure is made by forming a conductive mesh member in such a size that the periphery thereof is positioned outside of peripheral edges of transparent base plates so as to form margins when it is interposed therebetween, then folding the margins on the surface of one of the transparent base plates so that the margins function as conductive portions between the electromagnetic-wave shielding and light transmitting plate and the body of the equipment, and bonding the margins to the body of the equipment by pressure bonding.
Any combination of two transparent base plates and a conductive mesh member interposed therebetween allows the aforementioned structure in which the periphery of the conductive mesh member is positioned outside of peripheral edges of the transparent base plates so as to form margins which are then folded onto the surface of one of the transparent base plates so that the margins provide current conduction between the electromagnetic-wave shielding and light transmitting plate and the body of equipment. However, in case of two transparent base plates and a transparent conductive film interposed therebetween, the film may tear at the folded portions. In this case, therefore, the film cannot provide current conduction between the electromagnetic-wave shielding and light transmitting plate and the body of the equipment.
One of alternatives to the aforementioned transparent conductive film is a transparent conductive coating formed directly on an adhesive surface of one transparent base plate so that an electromagnetic-wave shielding and light transmitting plate is formed by the transparent base plate with the transparent conductive coating. However, in this case, the transparent conductive coating is covered by the other transparent base plate, thereby preventing the current conduction between the electromagnetic-wave shielding and light transmitting plate and the body of the equipment.
Therefore, in this case, design change is necessary, for example, making one transparent base plate in which the surface has a smaller area than that of the other transparent base plate so as to form an exposed portion of the transparent conductive coating, or forming a through hole in the transparent base plate to form a conductive path to the transparent conductive coating. Therefore, the assemblage of the electromagnetic-wave shielding and light transmitting plate and the installation thereof to the body of the equipment become complex.